Low Impact Development (LID)
What is LID?
The literature is full of terms such as “Smart Growth”, “Low Impact Development”, “Sustainable Development”, etc. All of these terms refer to stormwater management practices that promote the reduction of runoff volume from urban areas.
The goal of Low Impact Development (LID) is to allow for development of a site while maintaining as much of its natural hydrology as possible, such as infiltration, frequency and volume of discharges, and groundwater recharge.
In the LID approach, stormwater is managed in small, source control landscape features rather than in large, end-of-pipe pond structures located at the downstream extent of drainage areas. However, ponds may be required in addition to LID to create a “treatment train” effect. Through LID, hydrologic functions such as infiltration, peak and volume of discharges, and ground water recharge can be maintained with the use of reduced impervious surfaces, functional grading, open channel sections, disconnection and utilization of runoff, and the use of bioretention/filtration landscape areas.
With the LID approach, receiving waters experience little change in the volume, frequency, or quality of runoff or in the base flows fed by groundwater.
Developers, please consider LID when submitting your plans
- Stormwater quality needs to be addressed early in the design process. It is recommended that discussions regarding proposed BMPs occur early in each project between the developer’s planner and engineer and municipal staff.
- Take advantage of the entire site when planning for stormwater quality treatment.
- Implement source controls to prevent and minimize the discharge of pollutants.
- Incorporate stormwater treatment controls to remove pollutants from runoff.
- Minimize directly connected impervious areas.
- Maximize permeability at a project site.
- Select treatment areas that promote greater infiltration.
- Reduce runoff rates and volumes to more closely match natural conditions.
- Use drainage as a design element.
- Integrate stormwater quality management and flood control.
- Protect sensitive areas from encroachment.
- Design sustainable facilities that can be safely and economically maintained.
The LID design focus is to manage the stormwater as close as possible to its source—that is, on each individual lot rather than conveying the runoff to a larger regional pond.
Retrofitting sites to improve water quality is also essential to the health of our streams.